|Publication number||US8148203 B2|
|Application number||US 13/179,170|
|Publication date||Apr 3, 2012|
|Filing date||Jul 8, 2011|
|Priority date||Apr 27, 2006|
|Also published as||US7429772, US7439178, US7999348, US20070254457, US20070262378, US20080315345, US20110266659, WO2007127925A2, WO2007127925A3, WO2007127925B1|
|Publication number||13179170, 179170, US 8148203 B2, US 8148203B2, US-B2-8148203, US8148203 B2, US8148203B2|
|Inventors||Robin Wilson, Conor Brogan, Hugh J. Griffin, Cormac MacNamara|
|Original Assignee||Icemos Technology Ltd.|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (34), Non-Patent Citations (2), Classifications (7), Legal Events (1)|
|External Links: USPTO, USPTO Assignment, Espacenet|
This application is a divisional application of U.S. patent application Ser. No. 12/203,995, filed Sep. 4, 2008, currently pending, entitled, “Technique for Stable Processing of Thin/Fragile Substrates,” which is a continuation application of U.S. patent application Ser. No. 11/380,457, filed Apr. 27, 2006, now U.S. Pat. No. 7,429,772, entitled, “Technique for Stable Processing of Thin/Fragile Substrates,” the entire contents of all of which are incorporated by reference herein.
The present invention generally relates to a method of manufacturing a semiconductor device, and more particularly, to a method for using a silicon on insulator (SOI) semiconductor wafer for manufacturing devices having very thin and fragile substrates.
Semiconductor wafer fabrication generally refers to the process of making integrated circuits on silicon wafers. A typical semiconductor wafer is generally circular in plan view and has a diameter on the order of 25-300 millimeters (mm). Individual electronic circuits or devices are formed across at least one surface of the wafer and then the wafer is typically cut (sawed or diced) into a plurality of individual “dies” for packaging into individual integrated circuits (ICs).
Silicon on insulator (SOI) semiconductors, dielectric isolation (DI) semiconductors and bonded wafer semiconductor devices are generally known in the art. For example, basic known processes to bond semiconductor wafers include forming a layer of silicon dioxide on one silicon wafer, sometimes referred to as the “handle wafer” and placing the other wafer on the silicon dioxide and annealing (i.e., generally heating to and holding at a suitable temperature and then cooling at a suitable rate) the stacked wafers to form a bonded wafer semiconductor device having a buried oxide layer. Other methods of forming SOI semiconductor wafers are also known.
A handle wafer can be used to handle a semiconductor wafer during processing. Typically the device layer of semiconductor material is processed, e.g., trenched, implanted, doped, polished or the like, and is therefore moved from process to process. As device layers shrink or become more thin, they also become more fragile and hard to handle during processing.
Wafer sawing or dicing is a processing step that actually cuts the wafer into individual dies for assembly into IC packages. The wafer saw process typically includes mounting the wafer to a frame, cutting the wafer through its thickness according to the programmed die dimensions using a diamond cutting wheel rotating at a very high speed and cleaning the wafer using high pressure water spray. Alternately, wafers can be diced using a water-jet-guided laser. Improper wafer sawing can result in cracks in the wafers which is often referred to as die cracking. Even proper sawing may lead to die cracking in very thin wafers.
It is desirable to provide a technique to allow stable processing of thin and fragile semiconductor substrates. It is desirable to provide a method of manufacturing such thin semiconductor devices using SOI wafers and a deep trench etch. It is also desirable to provide a technique to manufacture larger diameter wafers with a lower level of breakage and/or die cracking.
Briefly stated, an embodiment of the present invention relates to a semiconductor on insulator (SOI) wafer that includes a semiconductor substrate having first and second main surfaces opposite to each other. A dielectric layer is disposed on at least a portion of the first main surface of the semiconductor substrate. A device layer has a first main surface and a second main surface. The second main surface of the device layer is disposed on a surface of the dielectric layer opposite to the semiconductor substrate. A plurality of intended die areas are defined on the first main surface of the device layer. The plurality of intended die areas are separated from one another. A plurality of die access trenches are formed in the semiconductor substrate from the second main surface. Each of the plurality of die access trenches are disposed generally at least partially beneath at least a respective one of the plurality of intended die areas.
Another embodiment of the present invention relates to a method of manufacturing semiconductor devices that includes providing a first semiconductor substrate having first and second main surfaces opposite to each other. A dielectric layer is formed on the first main surface of the first semiconductor substrate. A second semiconductor substrate is provided and the second semiconductor substrate has first and second main surfaces opposite to each other. The second semiconductor substrate is disposed on the dielectric layer opposite to the first semiconductor substrate. Portions of the first semiconductor substrate are selectively removed to form a plurality of die access trenches in the second main surface of the first semiconductor substrate. Each of the plurality of die access trenches defines at least a respective one of a plurality of intended die areas on the first main surface of the second semiconductor substrate.
The foregoing summary, as well as the following detailed description of the invention, will be better understood when read in conjunction with the appended drawings. For the purpose of illustrating the invention, there are shown in the drawings embodiments which are presently preferred. It should be understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown. In the drawings:
Certain terminology is used in the following description for convenience only and is not limiting. The words “right,” “left,” “lower,” and “upper” designate directions in the drawings to which reference is made. The words “inwardly” and “outwardly” refer to direction toward and away from, respectively, the geometric center of the object described and designated parts thereof. The terminology includes the words above specifically mentioned, derivatives thereof and words of similar import. Additionally, the words “a” and “and” as used in the claims and in the corresponding portion of the specification means “at least one.”
Although any particular embodiment of the present invention may refer to a particular conductivity (e.g., p-type or n-type), it will be readily understood by those skilled in the art that p-type conductivity can be switched with n-type conductivity and the device will still be functionally correct (i.e., a first or second conductivity type). Therefore, where used herein, the reference to n-type may be interchangeable with p-type and reference to p-type may be interchangeable with n-type.
Referring to the drawings in detail, wherein like numerals reference like elements throughout, there is shown in
Generally, device layers 24 having a thickness of 100 μm or less will be very fragile and will be well suited to handling during manufacturing using the SOI wafer 10 to provide more stability during processing and sawing/dicing. More stability of fragile device layers 24 will lead to higher production yields for a given size wafer dimension (e.g., 100 mm, 200 mm, 300 mm, etc.). Additionally, providing more stability for fragile device layers 24 will permit using larger overall wafer dimensions.
Optionally, the SOI wafer 10 is trenched to provide the plurality of die access trenches 20, but the device layer 24 is provided as a “blank” for customer end-processing. A “mask template” can be provided to the customer which corresponds to the plurality of die access trenches 20 so that the customer can customize any front-side device layer masks to their custom purpose. For example, the first semiconductor substrate 32 has first and second main surfaces 32 a, 32 b opposite to each other. The dielectric layer or buried oxide layer 35 is formed on the first main surface 32 a of the first semiconductor substrate 32. The second semiconductor substrate or device layer 24 is provided and the second semiconductor substrate 24 has first and second main surfaces 24 a, 24 b opposite to each other. The second semiconductor substrate 24 is disposed on the dielectric layer 35 opposite to the first semiconductor substrate 32. Portions of the first semiconductor substrate 32 are selectively removed to form the plurality of die access trenches 20 in the second main surface 32 b of the first semiconductor substrate 32. Each of the plurality of die access trenches 20 defines a respective one of a plurality of intended die areas 22 defined on or in the first main surface 24 a of the second semiconductor substrate 24.
The first main surface 32 a may be ground and/or polished flat using known processes, such as mechanical or chemical grinding, etching and/or polishing processes. Preferably, the handle wafer 32 is formed of silicon (Si). But, the handle wafer 32 may be formed of other materials such as gallium arsenide (GaAs), germanium (Ge) or the like. Preferably, the first main surface 32 a is ground and/or polished sufficiently to leave a polished, flat, clean surface, which is ideally defect free. The second main surface 32 b may be lapped and etched using a known lapping and/or etching process. The handle wafer 32 is then oxidized to form the buried oxide layer 35. The buried oxide layer 35 is applied using one of thermal growth, low pressure (LP) chemical vapor deposition (CVD), plasma enhanced chemical vapor deposition (PECVD), atmospheric pressure chemical vapor deposition (APCVD) and deposition. The buried oxide layer 35 is preferably formed of an oxide. Alternatively, the buried oxide layer 35 may be a nitride, silicon-oxynitride or other known dielectrics. The buried oxide layer 35 on the handle wafer 32 may be formed by any known technique.
The device layer 24 can be formed by bonding or otherwise forming a semiconductor layer on the buried oxide layer 35. Preferably, the device layer 24 is silicon. But, the device layer 24 may be formed of other materials such as gallium arsenide, germanium or the like. For example, the device layer 24 is typically a doped p-type or n-type silicon layer.
The SOI wafer 10, as shown in plan view in
Known processing techniques such as grinding, polishing and etching may be performed to obtain a desired thicknesses of the handle wafer 32, buried oxide layer 35 and device layer 24. Generally, semiconductor wafers 10 are coarsely thinned by a grinding machine having a rough grinding wheel or grinding pad such as a diamond or carbide wheel or pad having for example, diamond impregnated resin teeth. Grinding the wafer 10 also allows for thinner, and therefore, smaller IC packages. Generally, polishing is a finer process using a wet silica-particle slurry which is washed across the surface of the SOI wafer 10 at a predetermined flow rate and is referred to as chemical mechanical polishing (CMP). Optionally, surfaces of the SOI wafer 10 are thinned by grinding and then polishing.
The second main surface 32 b of the handle wafer 32 is masked and etched according to specific patterns (see e.g.,
Each of the die access trenches 20 in the handle wafer 32 exposes a backside of one of the respective intended die areas or dies 22. As best shown in the bottom plan view of
The plurality of die access trenches 20 may be formed in the second main surface 32B of the handle wafer 32 by a process such as plasma etching, reactive ion etching (RIE), sputter etching, vapor phase etching, chemical etching, deep RIE or the like. Utilizing deep RIE, die access trenches 20 can be formed having depths of about 40 to 300 μm or even deeper.
The intended die areas or dies 22 and the die access trenches 20 are depicted in
Optionally, a given die access trench 20 may provide access to more than one die 22.
Damage is more likely to occur to the SOI wafer 10 during sawing/dicing where loading changes dramatically, such as the transition between the exposed trench section 20 and the areas of remaining handle wafer 35. Accordingly,
From the foregoing, it can be seen that embodiments of the present invention are directed to methods for using a SOI semiconductor wafer for manufacturing devices having very thin and fragile substrates. It will be appreciated by those skilled in the art that changes could be made to the embodiments described above without departing from the broad inventive concept thereof It is understood, therefore, that this invention is not limited to the particular embodiments disclosed, but it is intended to cover modifications within the spirit and scope of the present invention as defined by the appended claims.
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|U.S. Classification||438/110, 257/E23.194, 257/499, 257/E21.214|